It seems both the Holiday Inn Select and Travelodge that are on the con site are already full. I'm not from Montreal and don't know much about the area, so can anyone tell me what other hotels there are that are close to the con (like within 10 min max walking distance)?

The Westin, InterContinental, Embassy Suites and Le Dauphin are next to the con. A bit further are the Hyatt and the Courtyard Marriott. Good luck for finding a room! If you have any further questions, I'll be happy to help.

We might have to consider the fact that it's the 150th anniversary of Montreal this year. There will be lots of events in the summer, meaning lots of tourists and lots of pre-booked hotels.

It really depends on how far you are willing to go and what price you are willing to pay... A bit further away, but still downtown and within walking distance of the convention, you have a bunch of hotels in the old port/old montreal or on the other side, you have the Queen Elizabeth hotel.You can also hit up some motels, inns or stuff like that.